The present disclosure relates to a fixing device fixing a toner image on a sheet and an image forming apparatus including this fixing device.
As one manner heating a fixing belt of a fixing device, a manner using a flat heater is known. As an example, the endless fixing belt with flexibility is sandwiched between the flat heater and a pressuring roller and is rotated by friction force at a pressuring area provided between the flat heater and the pressuring roller. The sheet having a transferred toner image is sandwiched between the heated fixing belt and the pressuring roller to be conveyed, and thereby, the toner image is fixed on the sheet.
Conventionally, with respect to such a heating manner using the flat heater, technique achieving excellent energy efficiency and uniformly outputting an image with a high gross level is examined. For example, a conventional fixing device is configured that a pressure between the fixing belt and the pressuring roller is increased from an entrance of a fixing nip (the pressuring area) and, in a sliding face composed of a plate heating body (the flat heater) and a heating body holder, the pressure is maximized at a downstream end of the sliding face in a moving direction of a recording medium.
However, in the above-mentioned conventional fixing device, because friction wear of an inner face of the fixing belt is progressed, it is feared that wear powder is mixed with lubricant to lower slidability. Moreover, because an outer diameter of the pressuring roller is suddenly varied at an exit of the pressuring area, it is feared that crumpling of the sheet and others occur to lower conveyance property.